Two-step sulphatizing roast



March 4, 1930. F. A. BRINKER I TWO-STEP SULPHA'TIZING ROAST Filed' oct. 21, 192e R. n 0 Y O r l m@ z M Y E. ,v R V n O N T /o M 15. n my? ,n n n .mm www B @mkb buwh,

I ythe1rindividual characteristics, will form APatented Mar.'4, `1.93() `1 UNITED s'rxrEsv PATENT OFFICE rnnnnmc A. BRINKER," oF SAN FRANCISCO, CALIFORNIA, AssIGNor:I or ONE-FOURTH 'ro JOSEPH P. RUTH, JR.,

OF DENVER COLORADO Two-STEP suLPIIATIzING RoAsT' Application led October 21; 1926. Serial No. 143,126.

This process relates to the formation of metallic sulphates from complex ores and the like, and reliesvupon the fact that ferrie oxide constitutes a catalyst for'the oxidation of sulfur dioxide to sulfur trioxide which latter combineswith `oxides to form sulphates.

The object of the invention is to provide a,

l sulphatizing process which will insure higher point.

extraction ythan heretofore, will more freely' sulphatize the various metals according to smallerA amounts of ferrites and thereby simplify and increase extraction, and will `be generally more economical as to fuel and the like. It is also an objectto provide a sulphatizingroast wherem the reactions may, if deslred, be carried beyond the sul'- phatizing pointtand yield a zinc oxide calcine which may betreated in' an acid leaching process to yield a more desirable calcine from a metallurgical and economical stand- The ro'cess is designed to fit the chemical i laws which govern the reactions of the different materials and to care for thewide-diiieru ence in ignition temperatures, formation temperatures, intensities and like conditions Y of the various constituents of various ores,

having in mindwhether the reactions are gas to gas, gas to solid, or solid to solid. The

process is applicable to all sulfide ores and concentrates containing zinc, lead, copper or other metals or mixtures thereof, in which iron sulfide is present or vto which it may be added.

Essentially, the process is a two-step roast,

. the first' step being a counter-current iron formation ofsulphates by the action of the S03 thus obtained. Sulfides of other metals such as lead and copper are desulfidized in both steps. The basis for the roast in these two stepsis the Wide difference between the conditions necessary to desulfidize the iron and condition the iron oxide t'o that` form best suited for catalysis of the 'sulfur dioxide, and the conditions necessary to desulfidize and sulphatize the zinc. Thus, the temperature -1n the rst step must be low -enough to pro- `duce ferrie oxide of proper condition which is too low to desuliidize the zinc and to form zinc ferrite and should be too low to form I zinc oxidecalcine by the addition of zinc sulfide to the zinc sulphate formed to convert all or a portion of the zinc sulphate along Withthe sulfide into such zinc oxide calcine. The' invention resides also in all the various noyel features, steps and combinations thereof as herein presented and described.

In the accompanying drawings there is represented diagrammatically one desirable type of apparatus and al method for carrying kon the invention, the manner of advancing the gases and solids and the primary reactions and conditions being indicated.

First step-counter-cuhent roast The first step is conveniently carried on in a vertical hearth furnace wherein the sulfide ore is fed at the top and discharged from the bottom, While 'air is admitted to'the lower portion ofthe furnace and travels upward in counter-current to the ore. Here the chief function is to Aroast the iro-n sulfide to ferriel oxide (FezOs) vof the best form for the subformed in the second step. To properly roastl Thesefconditions also avoid the formationl lof appreciable amounts of zinc ferrite,

' 550 C. and

sequent catalytic oxidation of S02v`to S08,

sincethat is the link which connects the: S02

liberated in the first step with the sulphates a cooling effect where it is most needed and serves as a means for controlling the intensity of oxidation on the upper hearths b'v supplying a deficiency of oxygen thereto. Also this air supply places the most oxygen where itl is needed to produce the best conditioned ferrie oxide, that is, on the lower hearths.

These conditions desulfidize all of the iron sulfide and-some of the lead and copper sulfides, but very little if any of the zinc sulfide.

Zn0.Fe2 03. Whereas, if this were a con current roast, the intensity would build up and-the temperature become so highl that the iron oxide would be poorly conditioned and subsequent catalysis would be poor. `Also some of the zinc would oxidize in a concuryrentroast and react withthe' ferrie oxide to form the insoluble ferrite which-is hard l to break later in'the roast and alsopcausesy ture may vary between 600 a very low yield of sulfur trioxide'. But in the counter-currenty low-temperature iron roast no zinc oxide will form and therefore no zinc ferrite.

The principal reactions in this step. are:

.Second step-econmtrrent ;m'stz'fng roastV The finishing roast. is` indicated as being performed in a tube furnace in which the gas'- to-s'olid reaction-of this step will take place 'very readily. The calcine from the iron roast, containing the catalytic ferrie oxide', zinc sulfide, and lead and copper sulfides and oxides and the like, is discharged into the upper end of the tube furnace, whileth'e sulfur ioxide and other gases from the iron roast,

vtogether with the required amount of air, are. also introduced into the upper end of said tube furnace and caused to move concurrently with the mineral. The reaction'here is highly oxidizing,

the reaction is dependent only upon contact between the gases and solids. The temperaandthe reactions proceed, very rapidly.

and if the ferric oxide has `been properly conditioned in the iron roast C. and 700 0.,."l

Thee-temperature may oxidized.J vthe catalytic influence of thefFe'zOa, the S02 is quickly oxidized to S03 `which in turn reacts with all ofthe metal oxides to form sulphates. `Zinc ferrite will not-be formed for two reasons: first, because the reaction ZnOrl-FegOaZnOFeaOa. isja solid-to-solid reaction for which there is not 4 proper Contact in this type ofl roast; second, because the zinc oxide will also, be in contact with S03 which will reverse 4the reaction to the point that the amount of ferrite formed will be negligible.

Theprincipal reactions taking place inithis step are:

i The flue dust, which comprises a small part of the total calcine and is settled out-of the iiue gases, is 'a roasted calcine readyfor leaching. This is an'advantage as it therefore is not necessary to return the du'st to the furnace for re-roasting.

' If zinc sulphate is to be [farmed only as an' thefurnacevand will give thevvlwell'known.l

reaction zns+3znsofizno+4soi This is', an endothermier'eacuon, which win not result in overheatingfany of thevpa'rticles and will not cause lowering of the extraction already made. Instead, thesame high extrac- .tion can be'obtained, and there will be a tendency tof'increase the tonnage which can be roasted per furnace. v The product`thusfobtained is a final calcine ready for leaching with acid.

In. general` The process is equally applicable lto any'v ore or product in whichI ironsu-lfide is present or to which it may be added,the desuldizing roast serving to form and 'condition the ferrie Voxide and the second roast serving to sulphatize all or a part of the `metallic contents.

The process is-'parfticularly suitable to ores high in copper, because heretofore large amounts of copper ferritehave been. formed v I by the processes employed; Whereas bythis f process theformation of copper ferrite may be held to a very low point merely by lower-V ing the temperature in both steps and thereby holdingfdown the intensities until. most of the sulfur has been driven off, whereupon the be increased and sulphatizinc sulfide and other' remainingsulfides are zation allowed to proceed at`the desired rate. `lao 4 The air introduced into the process may lie 3. A roast-ingrprocess for either cold or preheated, and all the air necessary for both roasting stepsmay be added in the iron'roast if combustion does not proceed Atoo freely.; otherwise or ifpreferredy the required amounts of air will be. supplied to the respective roasts.

I-claim: 1. A process for sulphatizing ores containing iron and other sulfides comprising two steps i'n the first of which the minerals are moved in contactwith the liberated gases at a temperature sufiicient for conversion of the iron sulfide and atleast portions of other sulfides but too low for the conversion of matefrial amounts of zinc sulfide, and in the second of which the minerals from the first step move concurrentlyv with the gases from the first stepand are sulphatized.

2. A two-'step roasting process for sulpha-4 tizing ores containing iron and zinc sulfides comprising moving the minerals countercurrent to the liberated gasesin the first step and/ desulfidizing the iron sulfide without desulfidizing the zincsulfide, and moving the calein'e'and gases from the first step concurliguircntly in the second stepwhereby the minerals are sulphatized.

sulphatizing ores containing iron sulfide and other minerals comprising two steps in the first of which the iron sulfideswoxidized to a catalytic 'ferrie oxide at a temperature too low for the conversion of material amounts of zinc sulfide, and

' wherein the minerals move countercurrent Ato the liberated gases, and in the second of which the minerals and gases from the first step move concurrently and 'the sulfur dioxide is converted to sulfur trioxide and the minerals sulphZd thereby.

4. A roasting processfor sulphatizing ores .containingiron sulfide and other minerals comprising two steps inthe first of which the minerals move'counter-currently to the liberated gases and the iron sulfide is oxidized and in Whichthe temperature is. maintained too low for the conversion of material amounts of zinc sulfide, and,l in the second of which I steps the minerals and gases from the first step are moved concurrently for the oxidation of SOzlto" S03 and in which the temperafor the formationl of large amounts of cata-- lytic ferrie oxide and too low for the conversion of appreciable amounts of zinc' sulfide, and in the second step the minerals and gases from lthe first step are moved concurrently for the catalytic conversion of sulfur dioxide to sulfur trioxide and at a temperature high enough for oxidation of the zinc sulfide and wherein the mineralsare sulphatized by action of the S03. r. 'v Y G. Aroasting process for sulphatizing ores containing iron, copper and zinc sulfides comprising two steps in the first of which the minerals are moved counter-currently to the lib-I erated gases at a temperature-'low enough to insure the formation of large amounts of cat# alytic ferrie oxide and too low for the formation of copper ferrite and conversion of apand the iron sulfide is oxidized and in which the temperature is maintained below approximately 550 C., and in the second of which steps the minerals and gases from the first .z

step are moved concurrently for the oxidation of sulfur dioxide to sulfur trioxide and in which the temperature is carried above 600o C. l

8. A twostep roasting process for sulphatizing ores containing iron and zinc sulfides comprising movingthe minerals countencurlrent toxthe liberated gases in the first step and desulfidizing the iron sulfide without desulfidizing the zinc sulfide, moving the calcine and gases from the first step concurrently in the second step whereby the minerals are sulphatized, and introducing zinc sulfideat. the end of this second step for reaction with the newly formed zinc sulfate to produce a 'calcined zinc oxide.

9. roasting' process for sulphatizing ores -containing iron sulfide-and Zinc sulfide comprising two steps in the first of which a tem- `perature is maintained low enoughfor the' formation of large amounts ofcatalytic ferric oxide andtoo low for the conversion of appreciable amounts of zinc sulfide, and in the second step the minerals and gases from the first step 4are moved concurrently for the catalytic conversion of sulphur dioxide to sulphur trioxide and at a temperature high enough for oxidation of the Zinc sulfide and wherein the minerals are sulphatized by the action of the S03.

fO. A roasting process for sulphatizing ores containing iron sulfide and zinc sulfide comprising two steps in the first o'fwhicha temperature is maintained low enough for' l'the formation of large amounts of catalytic .ferrie loxide and tool lowlgior the conversion of appreciable amounts of zinc sulfide, such temperature control being accomplished by maintaining a deficiency of oxygen, and in the second step the minerals and gases from the first step are moved concurrently for the catalytic conversion of sulphui' dioxide to sulphur trioxide andeat a, temperature high enough for oxidation of the zinc sulde and wherein the minerals are sulphatized by the etion of the S03. g

.In testimony whereof Iaixmy signature;

' FREDERIC A. BRINKER'. 

